x86/bitops: Use TZCNT mnemonic in <asm/bitops.h>

Current minimum required version of binutils is 2.25,
which supports TZCNT instruction mnemonic.

Replace "REP; BSF" in variable__{ffs,ffz}() function
with this proper mnemonic.

No functional change intended.

Signed-off-by: Uros Bizjak <ubizjak@gmail.com>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Cc: Andy Lutomirski <luto@kernel.org>
Cc: Brian Gerst <brgerst@gmail.com>
Cc: Juergen Gross <jgross@suse.com>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Josh Poimboeuf <jpoimboe@redhat.com>
Link: https://lore.kernel.org/r/20250325175215.330659-1-ubizjak@gmail.com

diff --git a/arch/x86/include/asm/bitops.h b/arch/x86/include/asm/bitops.h
index 100413aff6402e37acd4ef5b0c94e98e4d7a1e87..bbaf75ea6703bf767a34234d5ec48a9b8d16cada 100644 (file)
--- a/arch/x86/include/asm/bitops.h
+++ b/arch/x86/include/asm/bitops.h
@@ -248,7 +248,7 @@ arch_test_bit_acquire(unsigned long nr, const volatile unsigned long *addr)
 
 static __always_inline unsigned long variable__ffs(unsigned long word)
 {
-       asm("rep; bsf %1,%0"
+       asm("tzcnt %1,%0"
                : "=r" (word)
                : ASM_INPUT_RM (word));
        return word;
@@ -267,7 +267,7 @@ static __always_inline unsigned long variable__ffs(unsigned long word)
 
 static __always_inline unsigned long variable_ffz(unsigned long word)
 {
-       asm("rep; bsf %1,%0"
+       asm("tzcnt %1,%0"
                : "=r" (word)
                : "r" (~word));
        return word;